How accurate location can we get through an android device?

Question

I am using Android Location class to retrieve location from device. It gives location and Accuracy in meters .

I am using Samsung Galaxy S3. Getting below location details:
When I turn on Sim network and GPS , I can location as accurate as of 8 meters.
Surprisingly when I turn on GPS only, I can get location accuracy of say 36 meters.

My question is location accuracy depends on what?
Does it depend on a device(if its high quality device then good location accuracy) ?
Does it depend on county in which we are using device (depends on its phone or GPS network) ?
Or it depends on some thing else ?

Any inputs !!

Answer 1

In short it depends on BOTH

Your GPS give accurate results with help of Mobile Network and WIFI.

From Android official website "GPS, Cell-ID, and Wi-Fi can each provide a clue to users location. Determining which to use and trust is a matter of trade-offs in accuracy, speed, and battery-efficiency."

Does it depend on a device(if its high quality device then good location accuracy) ?

No, doesn't depend on device.

Does it depend on county in which we are using device (depends on its phone or GPS network) ? Or it depends on some thing else ?

Sort of, if you have good reception and connected to nearby wifi, your accuracy will be close.

Answer 2

GPS accuracy depends on:

1) Availability of assistance. You should be connected to WiFi or cell network so that latest satellite orbit models can be downloaded to the phone.

2) Signal strength. A stronger signal means (usually) better accuracy. More satellites means (usually) better accuracy. You must have the orbit model (aka ephemeris) for a satellite to use it.

3) Direct signal path to satellite. Bouncing signals add length to the path and dilute your position accuracy. Hard walls, water towers, metalized glass windows, all bounce GPS signals. If the reflection is stronger than the true signal, you can have a problem.

4) Antenna and RF path of the GPS inside the device. manufacturers who make good antennas get better performance because it gives a stronger signal for every satellite. Antennas that are directional or have large nulls are not good if pointed in the wrong direction.

5) Frequency stability of the oscillator in the handset. The oscillator is the reference to measure time delays. Every GPS receiver has one. Oscillators should change frequency only slowly (under 1 or 2 parts per billion in any given second). Oscillators hate heating, they hate electrical noise on their power supply, and a few other things. This is something designed into a phone, you can't change it. Putting the oscillator next to a power amp or SD card controller is a bad idea because they get hot.

The best GPS accuracy is obtained with an outdoor device, connected to a network for assistance, in an open field with good view of the sky. You should be 50 meters or more away from any building, wall, or surface that can reflect a signal. Salt water can also reflect signals, fresh water usually does not.

So that's the answer on GPS but it doesn't answer your full question. It sounds like the additional setting also uses some other positioning technology, probably WiFi. Try turning off the WiFi and see what kind of accuracy you get at the same time in the same location. WiFi can be very accurate, especially if there are multiple WiFi APNs that your phone can hear.